Holistic Conformal Coating Process

A successful holistic conformal coating process is never the result of a single step. It is the outcome of an aligned, end-to-end approach where PCB design, environmental demands, chemistry selection, application method, inspection strategy and production volume all work together. When these stages are synchronised, coating becomes predictable, repeatable and cost-efficient.

This guide outlines the holistic process model SCH uses to help OEMs and EMS providers implement stable, scalable coating processes across both liquid conformal coatings and Parylene.

A coating process can only be as good as the design it is applied to. Early Design-for-Conformal-Coating (DfCC) decisions reduce defects, masking time and rework.

• Keep-outs and maskable zones – define clearances around connectors, test points and mechanical interfaces.
• Component orientation – avoid shadowing and blocked vent paths. See: Component Selection & Orientation.
• Edge coverage & drain paths – minimise pooling and runs. Reference: Edge Coverage & Drain Paths.
• Material compatibility – understand how labels, adhesives and residues interact with the coating. See: Material Compatibility.

Explore the full Design Hub: Design for Conformal Coating Articles.

The operating environment should always drive coating chemistry selection. Choosing the right material early prevents long-term reliability issues and reduces total cost of ownership. For harsher or mission-critical environments, explore our Parylene solutions or the conductive polymer platform ProShieldESD.

Key environmental stressors:

• Humidity, condensation and contaminants
• Salt mist, SO₂/H₂S corrosion and harsh atmospheres
• Temperature cycling, vibration and mechanical flex
• Chemical, fuel, solvent or UV exposure
• High-voltage creepage and clearance requirements
  (see Clearance & Creepage Guide)

Your application method should match your volume, product mix and board complexity. Selecting the wrong method increases labour, rework and material usage. SCH supports both in-house automation and outsourced strategies with: coating application systems, Parylene deposition equipment, and full coating line design.

• Selective coating – ideal for medium–high volume automation.
• Manual spray – flexible for NPI, repair and small batches.
• Dip coating – excellent coverage when boards support drainage.
• Parylene deposition – 100% conformal and geometry-independent.

Compare all methods in the Coating Process Hub Overview.

Process drift frequently begins with the materials themselves. Small changes in viscosity, solvent balance, 2K mix ratios, temperature, humidity or cure profile can significantly alter wetting, flow and film formation.

As these parameters shift, edge coverage becomes less predictable, thickness distribution drifts, masking leaks appear and adhesion weakens. Without tight environmental and material control, a previously stable process will slowly move out of specification — creating defects that seem random but originate upstream. Robust material management is therefore central to any holistic coating process model.

Inspection confirms whether the process is performing as intended. SCH manufactures specialist UV Inspection Booths designed to highlight coverage, edge definition and UV contrast under controlled lighting.

Verification includes:

• Coverage and UV contrast inspection
• Thickness measurement using coupons
  (see Test Coupons & Witness Boards)
• Adhesion, hi-pot, salt-spray and environmental tests

Explore more in the Inspection & Quality Hub.

A coating process must evolve with changes in PCB design, material supply, production volume and field performance. Without structured feedback, even well-designed processes gradually drift away from their original intent.

SCH’s Conformal Coating Consultancy provides data-driven audits and full process reviews that examine every stage: design alignment, chemistry selection, masking strategy, application parameters, inspection methods, SPC trends and defect patterns. By analysing real production data, we identify root causes, remove unnecessary variation and develop targeted improvements that deliver higher yields, lower rework and more consistent long-term reliability.

For complex geometries, harsh environments or assemblies requiring long-term reliability, Parylene offers advantages liquid coatings cannot match. Vapour-phase deposition delivers pinhole-free, fully conformal coverage across sharp edges, cavities and dense 3D structures.

These properties make Parylene the preferred choice for aerospace, automotive, medical, sensing, defence and high-voltage electronics where failure is not an option.

Explore our full range of Parylene coating options and Parylene deposition systems to understand how vapour-phase deposition can solve coating challenges that liquids cannot.

Many coating failures arise from misalignment between design, process and chemistry — the leading cause of coating-related field returns. If the PCB layout does not support drainage, if incompatible materials or equipment are used, or if the chemistry does not match the environment, defects will occur regardless of operator skill.

A frequent issue is material and equipment incompatibility. When the coating is not suited to the application method — such as high-viscosity materials through fine spray valves, fast-flashing acrylics in high-airflow booths, or 2K systems without controlled mixing and induction — atomisation, flow and thickness become unstable. This drives higher material waste, more cleaning, downtime on the line and a rising cost-per-board.

The same applies when board design does not suit the chosen application method. Selective coating struggles with deep shadowing or dense assemblies; dip coating fails without drainage paths or when masking demand is excessive; and manual spray becomes slow and labour-intensive when keep-outs and orientations are poor. Misalignment between design and application method quickly leads to rework, leakage, pooling and uneven coverage.

Typical symptoms include dewetting, bubbles, fisheyes, pinholes, delamination, inconsistent thickness and chronic masking leakage. These issues often appear random, but almost always stem from upstream decisions around design, chemistry and equipment selection.

You can explore each defect category in more detail in our Common Coating Defects guide.

SCH supports OEMs and EMS with a full “total solutions” approach to conformal coating and Parylene — covering both in-house process development and fully outsourced production. Our goal is to ensure your coating strategy is technically sound, commercially viable and scalable from prototype to full volume.

For manufacturers running their own coating lines, we provide end-to-end engineering support: PCB design reviews, set up of conformal coating lines, Parylene deposition systems, masking optimisation, SPC/control planning, and operator training. We also support NPI programmes, helping teams validate chemistry, define masking strategies, optimise equipment parameters and benchmark new materials or processes before volume release.

For companies outsourcing coating, SCH delivers complete coating services across liquid chemistries and Parylene, backed by structured consultancy, specification development and detailed troubleshooting and failure analysis. Whether you need a short-term issue resolved or a long-term coating partner, we ensure your assemblies meet the required environmental and reliability demands.

Across all engagement levels, SCH offers tailored training and technical consultancy, including process benchmarking, troubleshooting, defect prevention, design-for-coating guidance and on-site or remote support for engineering and quality teams.

Whether you need technical guidance, equipment, production capacity, NPI validation or ongoing process improvement, SCH delivers end-to-end support across the entire coating lifecycle.

Find out more about our:

👉 Conformal Coating Solutions
👉 Parylene Solutions

Why Choose SCH Services?

Partnering with SCH Services means more than just outsourcing — you gain a complete, integrated platform for Conformal Coating, Parylene & ProShieldESD Solutions, alongside equipment, materials and training, all backed by decades of hands-on expertise.

• ✈️ 25+ Years of Expertise – Specialists in coating technologies trusted worldwide.
• 🛠️ End-to-End Support – Coating selection, masking, inspection and process validation.
• 📈 Scalable Solutions – From prototypes and NPI through to high-volume production.
• 🌍 Global Reach – Responsive support across Europe, North America and Asia.
• ✅ Proven Reliability – Built on quality, consistency and long-term customer partnerships.

📞 Call: +44 (0)1226 249019
✉ Email: sales@schservices.com
💬 Contact Us ›

Note: This article provides general technical guidance only. Final design, safety and compliance decisions must be verified by the product manufacturer and validated against the applicable standards.